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International Journal of Fluid Mechanics Research
ESCI SJR: 0.206 SNIP: 0.446 CiteScore™: 0.5

ISSN Печать: 2152-5102
ISSN Онлайн: 2152-5110

Выпуски:
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International Journal of Fluid Mechanics Research

DOI: 10.1615/InterJFluidMechRes.v29.i6.90
19 pages

Solutions of Polymers under the Conditions of Wall Turbulence. Mechanism of Drag Reduction

Volodymyr G. Pogrebnyak
Donbass State Academy of Building Industry and Architecture, Donetsk, Ukraine
Anatoly A. Pisarenko
Donbass State Academy of Building Industry and Architecture, Donetsk, Ukraine

Краткое описание

Results of a polarization-optical investigation of a wall turbulent flow of the solutions of polyethylene oxide (PEO) are presented in the paper. They prove that, within certain zones of the boundary layer, the macromolecules are subjected to a strong deformation effect of the hydrodynamic field. The experimental findings presented in the paper support the idea that the mechanism of drag reduction is uniquely related to the process of strong deformation of the macromolecules, which give rise to the nonlinear effects of elasticity. The adequate experimental verification of unrolling of the molecules under the conditions of wall turbulence illustrates that the employment of non-turbulent flows with stretching for studying the interaction between the macromolecules and the hydrodynamic field has some advantages. This allows an experimental investigation into the "anomalous" effects under the controlled conditions and provides a way of simulating the basic properties of the turbulent boundary layer. The velocity, velocity gradient fields and the degree of the unrolling of the macromolecules in the entry zone of a short capillary (under the modeled conditions of wall turbulence) are studied experimentally. If the flow is converging, the macromolecules are subjected to the considerable unrolling (up to 60 %) under the action of the hydrodynamic field, which leads to reconfiguration of this field. It is found that the behavior of the macromolecules in a flow with a longitudinal velocity gradient along with the effects of elastic deformations, which manifest themselves in this case, are essential for understanding of nature of the "anomalously" low turbulent friction observed in a flow of polymer solutions.


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